The present invention relates generally to painting of fabricated items, and more particularly to a method for manufacturing a painted body-in-white for an automotive vehicle.
As is known, one of the processes involved in the manufacture of automotive vehicles is the painting of what is termed the body-in-white. A body-in-white is the body shell for automotive vehicles prior to any further assembly of the vehicle, such as installation of the powertrain and interior. Typically, the body-in-white is assembled from metal parts. After the body-in-white is assembled, it is painted. Once painted, the remainder of the vehicle assembly operations, such as installation of the powertrain and the interior of the vehicle, are completed.
The painting process used to paint the body-in-white is one of the critical processes in the manufacture of an automotive vehicle. This painting process gives the automotive vehicle its color and also much of its corrosion protection and resistance. If the painting process is flawed, the vehicle""s color may fade over time, corrosion may occur more quickly, or the vehicle experiences other known painting process related problems.
The painting systems, usually termed paint shops, used to paint automotive vehicles are large, complex and expensive. Moreover, in the modem paint shops used to paint the body-in-white for automotive vehicles, controlling the emissions of volatile organic compounds and reducing the energy used is an ongoing challenge. Additionally, the number of paint layers have been increased to meet more stringent requirements, resulting in considerable additional complexity and expense in building and operating a paint shop.
Referring to FIG. 1, a generic manufacturing process 10 for manufacturing a painted body-in-white for an automotive vehicle is described. A vehicle body 11 is manufactured in a body shop 13 by fabricating body parts (not shown) at step 14 from galvanized and/or uncoated steel 12, usually in coil form and then assembling the vehicle body 11 by welding, fastening or adhesive bonding these parts at operation 16. Vehicle body 11 is now at the body-in-white stage.
After it is assembled, vehicle body 11 enters paint shop 19. Once entering the paint shop 19, vehicle body 11 is cleaned at cleaning station 20, which is typically one or more cleaning baths or spray tanks. After being cleaned, vehicle body 11 is phosphated by passing it through a phosphating bath or spray operation 22 where zinc phosphate is applied to vehicle body 11. As is known, the cleaning and phosphating operations are critical steps in the prior art paint processes because how well the body-in-white is cleaned and the quality of the zinc phosphate application significantly impact the corrosion protection that the painting process imparts to the automotive vehicle body as well as how well the paint adheres to the vehicle body. It is also well known that the cleaning and phosphating steps may consist of up to 10 or 12 individual treatment stations.
After the phosphating operation 22, the vehicle body 11 is passed through an e-coat operation 24 where e-coat is applied to the vehicle body 11. As is known, the e-coat application provides significant corrosion protection to the vehicle body 11. After the e-coat application, the e-coat is cured 26 by passing the vehicle body 11 through an e-coat oven 26. Next, the vehicle body 11 may be sanded and repaired at operation 28 and its seams sealed at seam sealer operation 30 by the application of a sealer to the seams of the vehicle body 11. The sealer is cured by passing the vehicle body 11 through a sealer oven 32. A primer is then applied to the vehicle body in primer paint booth 34. This primer can be a liquid primer or a powder coat primer. The primer is then cured by passing the vehicle body through a primer oven 36.
After the primer is cured, the primer may be sanded and/or repaired at operation 38 prior to the application of the color base coat. The color base coat is applied to the vehicle body 11 in base coat paint booth 40. In most cases, the color base coat is a liquid paint that emits volatile organic compounds which must be collected and processed with appropriate emission control systems. In some cases, such as in the painting of the metal part of the vehicle body for the Smart car manufactured by DaimlerChrysler A.G., a powder base coat is used. However, the use of powder base coats presents certain problems that aren""t presented by the use of liquid base coats, as will be discussed below. In cases where the base coat used is a waterborne paint, the vehicle body 11 is next dried by passing the vehicle body 11 through a base coat flash-off oven 42.
A clear coat is next applied to the vehicle body 11 in clear coat paint booth 44. After the clear coat is applied, the base coat and the clear coat are fully cured by baking the vehicle body 11 in a top coat oven 46. The color base coat and clear coat are often referred to collectively as the top coat. After the top coat is cured, the painted vehicle body 11 is inspected and any necessary finesse operations (touch up, etc.) carried out at operation 48. The painted vehicle body 11 is then ready for use in subsequent assembly operations to complete the assembly of a vehicle. Painted vehicle body 11 at the stage where it exits paint shop 19 and before any subsequent assembly operations is referred to as a painted body-in-white.
The color base coat, clear coat, and inspection and finesse operations typically consume more time than the steps preceding them. Consequently, many paint shops provide multiple paths for these operations, as shown in FIG. 1, to maximize the capacity of paint shop 19.
As can be seen, the painting process used to paint automotive vehicle bodies is complex. Further, the paint shops used to implement this process are often large and expensive. The cost of a paint shop used in the manufacture of high volume automotive can easily exceed several hundred million dollars.
It is an object of this invention to simplify the process used to manufacture painted metal body shells, such as a painted body-in-white, during the original equipment manufacture of the product in which the metal body is used, such as an automotive vehicle.
It is a further object of this invention to simplify the paint shop used to paint the body-in-white for an automotive vehicle.
It is another object of this invention to reduce the volatile organic compounds emitted during the painting of a vehicle body-in-white.
It is another object of this invention to reduce the amount of energy used during the painting of a vehicle body-in-white.
It is another object of this invention to reduce the number of paint layers applied in the paint shop.
It is another object of this invention to reduce the number of cleaning and pretreatment stations required.
A method of painting automotive vehicle bodies in accordance with this invention A method of manufacturing a body, preferably an automotive vehicle body, to have a plurality of coating layers, starts with assembling the body out of parts made from pre-coated metal, such as pre-coated galvanized steel. The galvanized steel may be produced either by the hot dip galvanized process or by the electrogalvanized process. Additionally the galvanized may be either a zinc or zinc alloy material.
After cleaning and pretreatment, a powder paint base coat is then applied onto the pre-coated metal of the vehicle body. The pre-coat layer is one of the plurality of coating layers and the powder paint base coat is another one of the plurality of coating layers.
In another embodiment, the powder paint base coat is applied in two steps, a first powder paint base coat and a finished color powder paint base coat. The first powder paint base coat is applied to a first portion of the vehicle body and the finished color powder paint base coat is applied to a second portion of the vehicle body. Unused first powder paint base coat and unused finished color powder paint base coat are both reclaimed, mixed, and the mixture used for at least some of the first powder paint base coat applied to the first portion of the vehicle body.